Interface between opto-electronic devices and fibers

ABSTRACT

An interface system includes separate optical and mechanical interfaces between opto-electronic devices and fibers. This allows each of these components to be optimized for there particular function. This also allows two surfaces to be provided for the optical interface, allowing the opto-electronic elements to be spaced further apart than the fibers. The interface system can be integrated together, used in conjunction with a conventional fiber housing, and can be surface mounted with an electrical interface.

CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] The present application is related to the commonly assigned,co-pending application entitled “Optical Subassembly”, attorney docketnumber DOC.052, filed concurrently herewith, the entire contents ofwhich are hereby incorporated by reference for all purposes.

FIELD OF THE INVENTION

[0002] The present invention is directed to interfacing opto-electronicdevices with fibers, particularly using separate elements for an opticalinterface and a mechanical interface.

DESCRIPTION OF RELATED ART

[0003] There are numerous ways to couple light to and fromopto-electronic devices and fibers. One typical manner in which this isachieved is to butt couple the opto-electronic devices right up againstthe end faces of the fiber. Such butt-coupling requires active alignmentto achieve desired levels of coupling efficiency. Further, butt-couplingdoes not allow the light beam to be modified. Finally, suchbutt-coupling typically requires close positioning of theopto-electronic devices in accordance with the spacing of the fibers,increasing crosstalk.

[0004] Another manner of achieving coupling between fibers andopto-electronic devices is to use short fibers, which in turn arecoupled to the fibers. This allows surface emitting opto-electronicdevices to be coupled with fibers, but still requires active alignment.

[0005] One passive alignment scheme proposed involves providing holes inall of the components to be aligned, e.g., a ferrule housing the fibers,a light coupling device including optics and a substrate including theopto-electronic devices. Pins are then inserted into the holes torealize alignment of all the elements. Such single shot alignment maynot be accurate enough for all applications. Further, the materialswhich can be used for the light coupling device are limited when theholes need to be provided therein. Finally, such alignment requires thatthere be a linear relationship among all of the components.

SUMMARY OF THE PRESENT INVENTION

[0006] The present invention is therefore directed to an interface whichsubstantially overcomes one or more of the problems due to thelimitations and disadvantages of the related art.

[0007] The above and other objects can be realized by providing aninterface system between an opto-electronic device and a fiber in ahousing including an optics block having at least one optical elementformed therein for coupling light between the fiber and theopto-electronic device and a mechanical interface, separate from theoptics block, at least part of the mechanical interface being disposedbetween the optics block and the housing, which aligns and mates thehousing and the optics block.

[0008] The opto-electronic device may include at least twoopto-electronic devices including an optical emitter and an opticaldetector. The opto-electronic device may include an array of identicalopto-electronic devices. The mechanical interface may surround theoptics block. The mechanical interface may be mounted on the opticsblock. The housing may include holes there through for receivingcorresponding pins therein and the mechanical interface further includesholes for receiving the pins. A spacer block may be provided between theoptics block and the opto-electronic device. An alignment plane of themechanical interface may be at an angle to a top surface of the opticsblock. A reflective surface may direct light between the optics blockand the mechanical interface. The mechanical interface may include anindentation which receives the optics block and an extension in theindentation to provide vertical spacing between the optics block and thefiber. The at least one optical element on the optics block mayhomogenize light.

[0009] The optics block and the mechanical interface may be made ofdifferent material. The optics block may be made from one of silicon andglass. The mechanical interface may be opaque at the wavelengths beingtransferred between the fiber and the optics block. The optics block mayinclude visual alignment features for aligning the optics block with themechanical interface. There may be mechanical mating features on theoptics block and corresponding mechanical mating features on themechanical interface for aligning the optics block and the mechanicalinterface.

[0010] The above and other objects may be realized by providing a systemincluding a housing having a fiber, an opto-electronic device, an opticsblock having two surfaces, the optics block coupling light between theopto-electronic device and the fiber, and a mechanical interface,separate from the optics block, at least part of the mechanicalinterface being disposed between the optics block and the housing whichaligns and mates the housing and the optics block.

[0011] The opto-electronic device may include at least twoopto-electronic devices and the fiber may include at least two fibers.The at least two opto-electronic devices may be a light source and alight detector. The at least two opto-electronic devices may include anarray of identical opto-electronic devices. The at least twoopto-electronic devices may be separated from each other in at least onedirection by more than the at least two fibers are separated from oneanother. The at least two opto-electronic devices are separated fromeach other in at least two directions by more than the at least twofibers are separated from one another in each respective direction. Thesystem may be surface mounted to an electrical interface.

[0012] A spacer between the optics block and the opto-electronic devicemay surround the opto-electronic device. A substrate may be providedwith both a bottom of the opto-electronic device and the spacer beingbonded to the substrate. The top surface of the opto-electronic devicemay be bonded to the spacer and the spacer further includesinterconnection tracks.

[0013] These and other objects of the present invention will become morereadily apparent from the detailed description given hereinafter.However, it should be understood that the detailed description andspecific examples, while indicating the preferred embodiments of theinvention, are given by way of illustration only, since various changesand modifications within the spirit and scope of the invention willbecome apparent to those skilled in the art from this detaileddescription.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The foregoing and other objects, aspects and advantages will bedescribed with reference to the drawings, in which:

[0015]FIG. 1A is an exploded elevational perspective view of aninterface of the present invention in conjunction with the fibers in ahousing and the opto-electronic devices;

[0016]FIG. 1B is an elevational perspective view of the system of FIG.1A;

[0017]FIG. 1C is a side view also illustrating internal features of thesystem of FIG. 1B;

[0018]FIG. 1D is an exploded front view also illustrating internalfeatures of the system of FIG. 1B;

[0019]FIG. 1E is a top view of the system of FIG. 1B;

[0020]FIG. 1F is a front view of the system of FIG. 1B;

[0021]FIG. 2A is an exploded elevational perspective view of an opticalsubassembly of the present invention;

[0022]FIG. 2B is an exploded side view of FIG. 2A;

[0023]FIG. 3A is an exploded perspective view of the fiber housing andan interface of the present invention;

[0024]FIG. 3B is an exploded side view of FIG. 3A;

[0025]FIG. 4A is a front view of another embodiment of the opticalinterface of the present invention;

[0026]FIG. 4B is top view of the opto-electronic devices in relation toalignment holes;

[0027]FIG. 5 is a cross-sectional side view of another embodiment of theinterface of the present invention;

[0028]FIG. 6 is a cross-sectional side view of another embodiment of theoptical subassembly of the present invention;

[0029]FIG. 7A is an elevational exploded view of another embodiment ofthe optical subassembly of the present invention; and

[0030]FIG. 7B is an exploded side view of the configuration shown inFIG. 7A.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0031] As can be seen in FIGS. 1A-1F, a plurality of fibers 10 areinserted into a ferrule 12. Opto-electronic devices 14 which are to bein communication with the fibers 10 are preferably provided on a siliconbench or sub-mount 16. In turn, this silicon bench 16 is preferablyprovided on a substrate 18. An optics block 20 provides at least oneoptical element between each opto-electronic device 14 and acorresponding fiber 10. The optics block 20 is preferably spaced fromthe opto-electronic devices 14 by a spacer 15. The optical elementspreferably include elements which collimate, focus and/or homogenize thelight. Since the optics block has two surfaces, two optical elements maybe provided thereon. Further, if required, additional optics blocks maybe bonded to and spaced from the optics block 20 to provide additionalsurfaces.

[0032] A mechanical interface 22 aligns the optics block 20, which isalready aligned with the optical devices 14 and with the mechanicalinterface 22, with the fibers 10. This may be achieved by alignmentfeatures on both the mechanical interface 22 and the ferrule 12 housingthe fibers 10. In the particular example shown, these alignment featuresconsist of holes 24 in the ferrule 12, which are already typicallypresent for aligning the ferrule with other devices, and alignment holes26 in the mechanical interface 22. Once these alignment holes 24, 26 arealigned, an alignment pin, not shown, may then be inserted therein tomaintain the aligned position.

[0033] The provision of separate elements to provide the mechanicalinterface and the optical interface provides several advantages. Forexample, the provision of the alignment holes 26 in the mechanicalinterface 22 allows the optics block to be made of a material selectedfor its optical properties. For example, the optics block may be made ofglass, which is preferable for forming optics therein. However, it isdifficult to accurately form cylindrical holes in glass. Thus, thismaterial would not be suitable if the holes had to be provided thereinas well, i.e., if the mechanical and optical interface were to berealized by single element. Further, since the mechanical interface isto accept the alignment pins, it must be of sufficient size toaccommodate the pins. Glass may be too fragile for such a purpose.Finally, glass is able to withstand the heat such as during soldering ofthe device to a printed circuit board or other electrical interface.Thus, the system may be surface mounted or pluggable to an electricalinterface.

[0034] The mechanical interface may similarly be made of a material bestsuited for its function. The mechanical interface 22 also preferablyincludes an aperture 28 which allows light to travel between theopto-electronic devices 14 and the fibers 10 without interference fromthe mechanical interface. This aperture also allows the mechanicalinterface to be made of any desired material, such as an opaque,thermally stable material in which holes may be accurately and easilyformed, such as a glass filled plastic, ceramic or molded plastic,without regard to the optical properties thereof.

[0035] Further, in the particular example shown, the aperture 28 is madelarge enough to surround the optics block 20, except for at a lip 30,which in turn provides the desired separation between a top of theoptics block 20 and an end face of the fibers. If the mechanicalinterface 22 is made of a material which is transparent to wavelengthsof light being exchanged between the fibers and the opto-electronicdevices, such an aperture 28 may no longer be needed. Some cut-out foraccepting the optics block 20, with the remaining portion serving as aspacer, may still be desirable. Either configuration will result in nophysical contact between the fibers 10 and the optics block 20.

[0036] The alignment for the entire structure is discussed below inrelation to FIGS. 2A-3. follows. FIGS. 2A-2B, show the alignment of theoptics subassembly including the optics block 20 and the opto-electronicdevices 14. First, the opto-electronic devices 14 are provided on thebench 16. Then, if the spacer 15 is being used, alignment features 34,such as fiducial marks, on the spacer 15 are aligned to alignmentfeatures 32, such as fiducial marks, on the bench 16. The spacer 15 isthen bonded, e.g., using solder or epoxy, into place on the bench 16.The bevels which can be seen on the interior surface of the spacer 15simply arise when using silicon as the spacer and the hole therein isformed by wet etching silicon along its crystalline plane. Whilewet-etching is a simple way of forming the hole in the spacer, verticalside walls may be more advantageous, e.g., for load bearing.Substantially vertical side walls may be realized by dry etchingsilicon. Further, other materials such as ceramic, glass, plastic, maybe used for the spacer 15. If the spacer 15 is transparent towavelengths of interest, the hole therein may not be required.

[0037] Then, alignment features 36, such as fiducial marks, on theoptics block 20 are aligned with the corresponding features on thespacer 15 and the bench 16 to align the optics block to theopto-electronic devices 14. The optics block 20 is then bonded intoplace, e.g., using solder or epoxy, on the spacer 15. The opticalelements on the optics block 20, as well as the alignment features 36,may be mass-produced on a wafer level and then diced to form individualoptics blocks. Thus, only the alignment of the optical block 20 isrequired to align all of the optical elements thereon with theopto-electronic devices 14.

[0038] Preferably, the alignment and bonding of the spacer and theoptics block occur on a wafer level, and then diced to form respectivedies which are then aligned to the bench 16. The alignment of the spaceris not very sensitive, i.e., the spacer just needs to be aligned so thatit does not block light between the optics block 20 and theopto-electronic device. While a spacer may be formed directly on theoptics block itself, the use of a separate spacer 15 allows largervertical separation to be achieved. The use of a separate spacer isparticularly advantageous when providing optical elements on a bottomsurface of the optics block 20, since the processes for forming theoptics and the spacer features interfere with each other. Finally, useof a separate spacer allows the sealing off of the opto-electronicdevice 14 to be more readily and stably achieved. Such sealing protectsthe opto-electronic device 14 from environmental factors, such ashumidity.

[0039] For certain wavelengths, e.g., in the near infrared, the opticsblock 20 may be made of another material, e.g., silicon. Then, all ofthe elements in the optical subassembly, i.e., the substrate, the spacerand the optics block, may be made of the same material, e.g., silicon.Making all of these elements of the same material reduces stress betweenthese elements due to a difference in the thermal coefficient ofexpansion.

[0040] Alignment of the optics block 20 to the mechanical interface 22and the fibers 10 is shown in FIGS. 3A-3B. While the optics block 20 hasalready been aligned with the opto-electronic devices 14, only theoptics block 20 is shown for simplicity. In the particular exampleshown, the optics block 20 is to be passively aligned with themechanical interface 22. Access holes 38 are provided in the mechanicalinterface to facilitate positioning of the optics block 20. When themechanical interface is not to surround the optics block, the accessholes 38 are not needed.

[0041] Such passive alignment may be realized using fiducial marksand/or mechanical mating features on the optics block 20 and the lip 30of the mechanical interface 22. The lip 30 provides an optical mountingsurface which maintains the optics block 20 at the desired distance fromthe end face of the fibers 10. Once aligned, the optics block 20, andthus the opto-electronic devices 14, are bonded to the mechanicalinterface 22. The mechanical interface 22, and all the components bondedthereto, are aligned to the housing 12 via alignment holes 24, 26 tocomplete the structure.

[0042] In addition to the passive alignment set forth above, in whichalignment features are provided on the elements being aligned, passivealignment may also be realized using an alignment template and/or usingthe position of the holes for receiving the pins in the mechanicalinterface. Further, active alignment may also be used.

[0043] An alternative embodiment is shown in FIG. 4A. Here, themechanical interface 22 does not surround the optics block, but ratheris positioned on top of the optics block 20. The aperture 28 and thealignment holes 26 are still part of the mechanical interface 22, butthe other features are not needed. Further, the alignment features maybe included on the body of the mechanical interface 22, since the lip isno longer present.

[0044] By utilizing both surfaces of the optics block 20, theopto-electronic devices 14 may be placed further apart, while stillrealizing a compact system for delivering light between theopto-electronic devices 14 and the fibers 10. Such placement may reducecross talk between the opto-electronic devices. As shown in FIG. 4A,assuming the opto-electronic devices are light emitters, optics 44 on afirst surface 42 of the optics block 20 collimates and deflects lightfrom the opto-electronic device 14. Optics 46 on a second surface 48 ofthe optics block 20 focuses light onto the fiber 10. Obviously, if theopto-electronic devices are detectors, the functioning of the opticswould be reversed.

[0045] The ability to place the opto-electronic devices further apartthan the fibers is particularly advantageous when the system is atransceiver system, i.e., there is at least one light emitter and atleast one light detector. This spacing may be further enhance byadditionally separating the emitter and detector in a directionorthogonal to the direction shown in FIG. 4A. Such a configuration isshown in FIG. 4B, where a light emitter 50 is separated from a lightdetector 52 in two directions. While these elements are still betweenthe alignment holes 24, 26, they are further apart than the fibers 10and are also separated an orthogonal direction. Such separationminimizes crosstalk, while maintaining the original profile. Further,this separation can be realized even when the optics block is not largerthan the mechanical interface.

[0046] A configuration employing the interface of the present inventionwhere the fiber housing is positioned orthogonally to the plane of theopto-electronic devices is shown in FIG. 5. The alignment holes 24, 26are still used to align the fiber housing 12 and the mechanicalinterface 22, the mechanical interface 22 is now aligned to the side ofthe optics block 20. In order to direct light between the fibers and theopto-electronic devices 14, a reflective surface 60 is provided. Asshown in FIG. 5, this reflective surface 60 may be formed in glass orother materials. A metal coating may be provided on this surface toenhance the reflectivity thereof. The material having the reflectivesurface may then be bonded to a top surface of the optical block 20.

[0047] In the particular example shown in FIG. 5, the opto-electronicelement 14 is a VCSEL and another opto-electronic element 14′ is a powermonitor for monitoring the power output by the VCSEL. A first element 62on the optics block 20 splits off and collimates part of the beam outputby the VCSEL and directs it to the power monitor 14′. A second opticalelement 64 may be provided on the optics block 20 to focus the lightonto the power monitor 14′. Details of such a configuration are setforth in commonly assigned, co-pending U.S. patent application Ser. No.09/386,280 entitled “Diffractive Vertical Cavity Surface Emitting LaserPower Monitor and System” the entire contents of which are herebyincorporated by reference for all purposes.

[0048] Meanwhile, the undeflected portion of the light travels to athird optical element 66, where it is focused onto the fiber, afterbeing reflected by the reflective surface 60. Thus, in accordance withthe present invention, alignment may be realized using the alignmentholes already available on the fiber housing without requiring that thecomponents all be in the same plane. While a VCSEL array is discussedabove, a detector array could be similarly positioned.

[0049] While all the previous configurations have illustrated theopto-electronic devices bonded on the bottoms thereof to a substrate 16,thereby requiring wire-bonding to realized their required electricalconnections, FIGS. 6-7B illustrate bonding the top of theopto-electronic devices to the optics block. Since all theinterconnections on the typical opto-electronic devices are provided onthe top thereof, such bonding allows the use of wire bonding to beeliminated, which in turn allows more compact interconnections to berealized.

[0050] As shown in FIG. 6, the interconnections to the opto-electronicdevice 14 can be realized using a pair of flex leads, a signal flex lead72 and a ground flex lead 74. An interconnect spacer 70 serves the samefunction as the previous spacer 15, but also includes interconnectiontracks for connecting the opto-electronic element 14 to the signal flexlead 72. If space permits, interconnection tracks for the ground flexlead 74 may also be provided on the interconnect spacer 70. Otherwise,the ground flex lead 74 may be attached to the bottom of theopto-electronic device 14, as shown in FIG. 6. While shown as a separateelement in FIG. 6, the interconnect spacer 70 may be integral with theoptics block 20. The opto-electronic device preferably is mounted on aheat sink block 78. Thus, the module can be surface mounted or pluggedinto an electrical interface, e.g., a printed circuit board or flexcircuit, without additional housing which may be needed to connect thewire bond configurations discussed above.

[0051] As shown in FIGS. 7A and 7B, another configuration eliminatingthe need for wire bonds includes again providing the interconnect spacer70 to which the opto-electronic device 14, here a VCSEL array, isbonded. While shown as a separate element in FIGS. 7A and 7B, theinterconnect spacer 70 may be integral with the optics block 20.Instead, of connecting the opto-electronic device 14 to flex leads, theinterconnect spacer 70 now includes metal lines 80 on a bottom surfacethereof, extending from the opto-electronic device 14. A chip carrier86, preferably ceramic, has a hole 84 therein for receiving theopto-electronic device 14 therein. The chip carrier 86 is preferablyattached to the spacer 80 using a sealing ring 88, e.g., anyconventional adhesive.

[0052] The chip carrier 86 also includes a connection region 82 withvias to connect the metal lines 80 to the outside, e.g., through abottom surface of the chip carrier. This may be accomplished, forexample, using holes 90 through the chip carrier lined with metal. Thus,the module can be surface mounted or plugged into an electricalinterface, e.g., a printed circuit board or flex circuit, withoutadditional housing which may be needed to connect the wire bondconfigurations discussed above. While the configuration shown in FIGS.7A and 7B has assumed all required connections for the opto-electronicdevice are on the top surface thereof, a ground connection could also beprovided on the bottom surface.

[0053] When using a spacer which is transparent to wavelengths ofinterest and in the path of the radiation, such as shown in FIGS. 6-7B,the spacer may have optical elements formed thereon. For example, if thespacer and the optics block are made of the same material, there willnot be an optical interface between them. Thus, a bottom surface of thespacer can be used on a second optical surface. The opto-electronicdevice could be slightly removed from this bottom surface even whenbonded to the bottom surface, for example, providing a thick enoughlayer of bonding material. If a separate spacer is not used, theopto-electronic device may still be attached to the bottom of the opticsblock with this bonding spacing such that the optics block stillprovides two surfaces. If the spacer and the optics block are made ofdifferent material, optics may be provided on either surface of thespacer. Of course, additional optics block may be bonded together toprovide the surfaces needed, but with a commensurate increase inthickness of the system.

[0054] It is further noted that the any of the individual componentsdescribed in connection with a particular embodiment may be used withother configurations. For example, the opto-electronic device 14 asshown in FIGS. 6-7B, may be bonded to the bottom of the optics block inthe configuration of FIGS. 1-2A.

[0055] While the present invention is described herein with reference toillustrative embodiments for particular applications, it should beunderstood that the present invention is not limited thereto. Thosehaving ordinary skill in the art and access to the teachings providedherein will recognize additional modifications, applications, andembodiments within the scope thereof and additional fields in which theinvention would be of significant utility without undue experimentation.Thus, the scope of the invention should be determined by appended claimsand their legal equivalents, rather than by examples given.

What is claimed is:
 1. An interface system between an opto-electronicdevice and a fiber in a housing comprising: an optics block having atleast one optical element formed therein for coupling light between thefiber and the opto-electronic device; and a mechanical interface,separate from the optics block, at least part of the mechanicalinterface being disposed between the optics block and the housing, whichaligns and mates the housing and the optics block.
 2. The interfacesystem of claim 1, wherein said opto-electronic device comprises atleast two opto-electronic devices comprise an optical emitter and anoptical detector.
 3. The interface system of claim 1, wherein saidopto-electronic device comprises an array of identical opto-electronicdevices.
 4. The interface system of claim 1, wherein said mechanicalinterface surrounds said optics block.
 5. The interface system of claim1, wherein said mechanical interface is mounted on said optics block. 6.The interface system of claim 1, wherein the housing includes holesthere through for receiving corresponding pins therein and saidmechanical interface further comprises holes for receiving the pins. 7.The interface system of claim 1, further comprising a spacer blockbetween the optics block and the opto-electronic device.
 8. Theinterface system of claim 1, wherein an alignment plane of themechanical interface is at an angle to a top surface of the opticsblock.
 9. The interface system of claim 8, further comprising areflective surface directing light between the optics block and themechanical interface.
 10. The interface system of claim 1, wherein themechanical interface comprises an indentation which receives the opticsblock and an extension in the indentation to provide vertical spacingbetween the optics block and the fiber.
 11. The interface system ofclaim 1, wherein said at least one optical element on the optics blockhomogenizes light.
 12. The interface system of claim 1, wherein saidoptics block and said mechanical interface are made of differentmaterial.
 13. The interface system of claim 1, wherein said optics blockis made from one of silicon and glass.
 14. The interface system of claim1, wherein said mechanical interface is opaque at the wavelengths beingtransferred between the fiber and the optics block.
 15. The interfacesystem of claim 1, wherein said optics block comprises visual alignmentfeatures for aligning the optics block with the mechanical interface.16. The interface system of claim 1, further comprising mechanicalmating features on the optics block and corresponding mechanical matingfeatures on the mechanical interface for aligning the optics block andthe mechanical interface.
 17. A system comprising: a housing having afiber; an opto-electronic device; an optics block having two surfaces,said optics block coupling light between the opto-electronic device andthe fiber; and a mechanical interface, separate from the optics block,at least part of the mechanical interface being disposed between theoptics block and the housing which aligns and mates the housing and theoptics block.
 18. The system of claim 17, wherein said opto-electronicdevice comprises at least two opto-electronic devices and the fibercomprises at least two fibers.
 19. The system of claim 18, wherein saidat least two opto-electronic devices comprise a light source and a lightdetector.
 20. The system of claim 18, wherein said at least twoopto-electronic devices comprise an array of identical opto-electronicdevices.
 21. The system of claim 18, wherein said at least twoopto-electronic devices are separated from each other in at least onedirection by more than said at least two fibers are separated from oneanother.
 22. The system of claim 21, wherein said at least twoopto-electronic devices are separated from each other in at least twodirections by more than said at least two fibers are separated from oneanother in each respective direction.
 23. The system of claim 17,further comprising a spacer surrounding the opto-electronic device. 24.The system of claim 17, further comprising a substrate, both a bottom ofsaid opto-electronic device and the spacer being bonded to thesubstrate.
 25. The system of claim 17, wherein a top surface of saidopto-electronic device is bonded to the spacer and the spacer furthercomprises interconnection tracks.
 26. The system of claim 17, whereinthe system is surface mounted to an electrical interface.